Dry cleaning method and composition



United States Patent O 3,335,091 DRY CLEANING METHOD AND COMPOSITIONHerman Spencer Gilbert, Angleton, Tex., assignor to The Dow ChemicalCompany, Midland, Mich., a corporation of Delaware No Drawing. FiledFeb. 8, 1965, Ser. No. 431,182

3 Claims. (Cl. 252-153) The present invention relates to a new -drycleaning method and compositions for use therein. More specifically, thepresent invention is concerned with a method for decreasing the amountsof metallic ion impurities introduced into the solvent systems generallyemployed in dry cleaning processes. I

It has been discovered that the presence of polyvalent metal ions in drycleaning solvent systems is detrimental to the eifectiveness andefficiency of *dry cleaning operations. This surprising and unexpecteddiscovery resulted from observations that the reflectance readings ofcloth samples were influenced by the polyvalent metal ion content of thedry cleaning solvent system in which the samples had been cleaned. Itwas found that reduction of the polyvalent metal ion content of asolvent system improved the brightness (as indicated by higherreflectance readings) of fibrous materials cleaned therein.

In the method of the present invention, a protective coating is impartedto those metallic surfaces of a dry cleaning apparatus which come intocontact with the solvent system used in the dry cleaning process,advantageously by reaction between a compound dissolved in the solventsystem and said metal surfaces whereby a surface coating non-reactivewith the solvent system is formed. This protective coating inhibits theintroduction of metallic impurities from the metal surfaces to theconice contacting dry cleaning solvent system is also demonstrated.

Example 1 After the discovery that polyvalent metal ions tend to bedeposited from dry cleaning solvent systems onto materials cleanedtherein and that such deposits adversely affect the brightness of thecleaned materials, experiments were conducted to determine quantitativeeffects of this unexpected phenomenon. Investigation revealed that thepolyvalent metal ion deposit is frequently heaviest where moisture ispresent in the material. Moisture, of course, is normally present inmaterials being cleaned and additional moisture is generally present inthe formulated dry cleaning solvent initially introduced into the drycleaning system.

A series of forty loads of clothes, averaging about eight pounds perload, were cleaned in a regular commercial dry cleaning machineemploying a standard perchloroethylene dry cleaning solvent system usedin the cleaning industry. A number of new, 4" by 11" swatches of cotton,wool, viscose taffeta and spun acetate materials were cleaned togetherwith this series of loads of clothes and the deposit of polyvalent metalions thereon was determined by emission spectroscopy. A portion of eachof the swatches was moistened with a few drops of deionized water priorto each cleaning cycle to demonstrate the effect of moisture, present inthe material being cleaned, on the tendency of the metal ions to depositon the cloth. The original metal content of these new swatches providesa standard for determination of the amounts of metal deposited duringcleaning. The results are shown in Table I, below, where metal contentis reported as parts per million (ppm) based on the cloth analyzed.

TABLE I Metal Content (p.p.m.) Swatch Description Ca Mg Fe Cu Ti Zn PbCd Cotton New 47 15 14 1 5 20 10 23 Wet area 420 27 25 35 10 30 24 Dryarea 160 21 22 33 13 42 30 20 Wet-dry interface 800 55 47 15 340 65 WoolNew 56 7 14 1 1 47 2 2 Wet area- 50 1. 5 12 40 10 220 12 36 Dry area 526 13 1 9 40 9 6. 5

Viscose taffeta New 500 48 13 1 20 35 3 Wet area- 330 30 12 35 70 15 Dryarea 520 65 28 12 20 5O 13 Spun Acetate- New. 48 2 1 20 10 2 Wet area".150 34 2 1 20 10 16 Dry area 230 70 30 1 20 10 10 tacting solvent systemand materials cleaned therein show significantly and consistently higherreflectance readings than those obtained when no such protective coatingis provided.

In general dry cleaning practice a solvent system comprising essentiallyan organic dry cleaning solvent is employed, e.g., chlorinatedhydrocarbons such as perchloroethylene, trichloroethylene and the like,or volatile hydrocarbons such as benzene, naphtha and the like, and isfrequently formulated to contain detergents or soaps and otheradditives. The term solvent system is used herein to designate thesecommonly used solvents and formulated solvents.

The following examples illustrate the detrimental effect on thebrightness of materials caused by deposition of polyvalent metal ionsonto the material. The tendency of polyvalent metal ions to deposit onmaterials from the Example 2 This expediment illustrates the correlationbetween reflectance loss and the presence of polyvalent metals in a drycleaning solvent system used to clean swatches of material.

A series of cloth swatches was agitated for extended time periods inquantities of three different commercially available dry cleaningsolvent systems. In each case the reflectance readings of swatchesagitated in samples of the new, uncontaminated dry cleaning solventsystem were compared with reflectance readings of swatches agitated inportions of the same dry cleaning solvent system which had beensaturated with Zn, Cu, Fe, and Mg ions. These saturated portions wereprepared by extended stirring of water soluble salts of these metalspecies with the dry cleaning solvent employed. The reflectancereadings, taken on a standard reflectometer, are tabulated in Table II,below, as taken initially and at the end of one, two and three days ofagitation in the solvent. In the following table, Solvent 1 isperchloroethylene; Solvent 2 is a chlorinated hydrocarbon dry cleaningsolvent, containing a petroleum sulfonate base detergent, widely used incommercial, coin-operated, dry cleaning machines; Solvent 3 is aformulated perchloroethylene solvent containing a phosphate basedetergent additive.

TAB LE II.REFLECTANCE READINGS 1 day 2 days 3 days Spun AcetateSwatches: 1

Solvent 1:

(Metals absent) 84.5 84. 5 84. 5 (Metals present) 84. 82. 81. 5 Solvent2:

(Metals absent) 84. 5 84. 0 84. 0 (Metals present) 83.0 80.5 78. 5Solvent 3:

(Metals absent) 83. 5 83.0 83.0 (Metals present) 82.0 78. 5 78. 5Worsted Gabardine Wool Swatches: 2

Solvent 1:

(Metals absent) 73.0 73.0 73.0 (Metals present) 70. 0 68.0 67. 5 Solvent2:

(Metals absent) 73.0 72.5 73.0 (Metals present)..- 71.5 67. 5 65.0Solvent 3:

(Metals absent) 72.5 72.5 72. 5 (Metals present) 71.0 69. 5 69. 5

l Initial reflectance reading 85 units.

1 Initial reflectance reading 73.5.

As shown by the comparative reflectance readings in Table II, above, thepresence of the polyvalent metal ions (which were the only contaminantspresent in the test samples of solvent) causes a significant loss ofwhiteness in the swatches.

In practice of the method of the present invention, metal surfaces of adry cleaning apparatus which are exposed to the solvent system arecontacted with a corn pound capable of forming a protective metalsurface coating which inhibits the previously discussed introduction ofmetallic impurities into the solvent system. Examples of such compounds,conveniently employed as additives to the solvent system used in the drycleaning apparatus, include formic acid, acetic acid, propionic acid,butyric acid, dimethyl hydrogen phosphite, diethyl hy drogen phosphite,dipropyl hydrogen phosphite, dibutyl hydrogen phosphite, dimethyl monoacid orthophosphate, diethyl mono acid orthophosphate, dipropyl monoacid orthophosphate, dibutyl mono acid orthophosphate, 4,4-dithiodimorpholine, 2,2-dithiobisbenzothiazole and mixtures thereof. Aquantity of from about 1 to 50 parts by weight of one or more compoundsselected from the above group is added to 1000 parts by weight of a drycleaning solvent system to furnish a new composition of the presentinvention. This solvent system, as previously noted, comprisesessentially an organic dry cleaning solvent base selected from volatilehydrocarbons and chlorinated hydrocarbons well known to the art. Inaddition there may be present relatively small amounts of otheradditives such as soaps or detergents, water, anti-redeposition agents,brighteners, anti-static agents, etc. While these relatively smallamounts of additives have no marked effect on the formation of theprotective metal coating, each plays a role in improving or providingother desirable features in a dry cleaning process. The new compositionsof the present invention, which consist essentially of a major amount ofa dry cleaning solvent and a minor amount in the range of from about 0.1to 5.0 weight percent of one or more of the previously listed compoundswill therefore usually contain small amounts of one or more detergents,water, and other agents as described above.

The following examples describe completely representative specificembodiments of the method and compositions of the present invention,These examples, however, are not to be interpreted as limiting theinvention other than as defined in the claims.

Example 3 A galvanized metal test coupon, approximately /2 x /2 square,was immersed for several days in a sample of a commercially available,perchloroethylene base, dry cleaning solvent system after addition of 1part by weight of acetic acid to 1000 parts by weight of the solventsystem. The solvent system, widely used in commercial, coin-operated drycleaning machines, contained small amounts of a petroleum sulfonate basedetergent and water. An adherent protective coating, presumably zincacetate, was formed on the galvanized metal test coupon by thistreatment. A control coupon was prepared by the same treatment butomitting the acetic acid addition. The test and control coupons werethen agitated for extended periods of time in separate 100 ml. portionsof the solvent system described above which also contained swatches ofcotton cloth. Table III, below, shows the reflectanc readings of suchcotton swatches after four, six and seven day periods of agitation inthese solvent systems containing either the control or test coupons. Theinitial reflectance readings of the cotton swatches, before treatment inthe solvent system, was units. Reflectance measurements were made on astandard reflectometer.

As indicated by the data above, the presence of a protective coating onthe galvanized metal coupon in contact with the solvent system inhibitedthe introduction of polyvalent metal ions into the solvent system. Thisis shown by the higher reflectance readings of the cotton swatches inthe test run as compared to those in the control run.

Example 4 In this experiment a piece of copper wire (5.7 grams) wasimmersed for 24 hours in 50 mls. of perchloroethylene containing 1 ml.of acetic acid. An identical piece of copper wire was immersed for thesame length of time in 50 mls. of perchloroethylene which contained noacetic acid. These two pieces of wire were rinsed with freshperchloroethylene and placed in perforated polyethylene bags. Each bagwas placed in separate portions of the solvent system used in Example 3,above, which also contained 2" x 2" cotton swatches. A controlexperiment containing no copper wire was also conducted. Table IV,below, shows the reflectance readings of cotton swatches removed fromthe three portions of solvent system after agitation therein for twelvedays.

TABLE Iv Reflectance readings Description: after 12 days No Cu wirepresent 69.8 Untreated Cu wire present 67.8 Treated Cu wire present 69.4

The above data show (1) the adverse effect on brightness of the clothwhen copper metal is in contact with the solvent system employed to dryclean cloth, and (2) the inhibition of this adverse effect by treatmentof the copper metal to form a protective coating.

Example 5 In the following experiment a series of galvanized metalcoupons were immersed in portions of the solvent system described inExample 3, above, which contained 1000 ppm. (based on the weight of thesolvent system employed) of various additives. These additives providedprotective coatings on the coupons. Each coupon was immersed for elevendays in an additive-containing solvent system and then rinsed and dried.Each treated coupon (2" x /2" x was then agitated for five days in 100mls. of fresh solvent system containing 2" x 2" cotton swatches. Controlexperiments employing (1) an untreated coupon and (2) a coupon immersedfor eleven days in perchloroethylene containing no additive, were alsorun. Table V, below, shows the reflectance readings of cotton swatchesafter five days agitation in the described solvent system.

In each case, above, treatment of the galvanized metal coupon with theindicated additive produced a protective metal coating. The uniform andconsistent improvement in reflectance readings of cotton swatchesagitated in solvent systems exposed to such coated metals as compared touse of non-coated metals demonstrates the value of such treatment ofmetal surfaces exposed, in a dry cleaning apparatus, to the solventsystem. In the preceding experiments (Examples 3, 4 and 5) glasscontainers were employed to hold the solvent systems.

In the manner of Example 5, above, treatment of metal surfaces exposedto a solvent system in dry cleaning operations with formic acid,propionic acid, butyric acid, dimethyl hydrogen phosphite, dipropylhydrogen phosphite, dibutyl hydrogen phosphite, diethyl mono acidorthophosphate, or dipropyl mono acid orthophosphate produces similarlyadvantageous results, i.e., a protective coating is formed on suchexposed metal surfaces which decreases polyvalent metal ion content ofthe contacting solvent system by inhibiting the introduction of metalspecies into the solvent system. In each case the improvement in thebrightness of clothes cleaned in a solvent system which is in contactwith metal surfaces containing a protective coating as previouslydescribed in significant and consistent.

I claim:

1: In a method for cleaning textile materials with an organic drycleaning fluid employing a metallic apparatus for containing the saidfluid and the textile, the improvement for increasing the brightness ofthe textile which comprises maintaining in contact with the surfaces ofthe metallic apparatus a solution of from 0.1 to about 5.0% by weight ofat least one member selected from the group consisting of formic acid,acetic acid, propionic acid, butyric acid, 4,4-dithiodimorpholine,2,2'-dithiobisbenzothiazole and mixtures thereof, in a dry cleaningsolvent.

2. An improved dry cleaning solvent composition which consistsessentially of amajor amount of a dry cleaning solvent and a minoramount in the range from about 0.1 to 5 weight percent of4,4'-dithiodimorpholine.

3. An improved dry cleaning solvent composition which consistsessentially of a major amount of a dry cleaning solvent and a minoramount in the range from about 0.1 to 5 weight percent of2,2'-dithiobisbenzothiazole.

References Cited UNITED STATES PATENTS 2,507,984 5/ 1950 Keuntzcl 2521432,517,893 8/1950 Larcher 252-171 X 2,729,576 1/ 1956 Trusler. 2,852,4719/ 1958 Atkins et a1. 252-171 2,904,514 9/1959 Nusselein 2521713,057,676 10/1962 Wedell.

FOREIGN PATENTS 3 09,314 4/ 1929 Great Britain. 912,118 12/ 1962 GreatBritain.

LEON D. ROSDOL, Primary Examiner. J. T. FEDIGAN, Assistant Examiner.

1. IN A METHOD OR CLEANING TEXTILE MATERIALS WITH AN ORGANIC DRYCLEANING FLUID EMPLOYING A METALLIC APPARATUS FOR CONTAINING THE SAIDFLUID AND THE TEXTILE, THE IMPROVEMENT FOR INCREASING THE BRIGHTNESS OFTHE TEXTILE WHICH COMPRISES MAINTAINING IN CONTACT WITH THE SURFACES OFTHE METALLIC APPARATUS A SOLUTION OF FROM 0.1 TO ABOUT 5.0% BY WEIGHT OFAT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF FORMIC ACID,ACETIC ACID, PROPIONIC ACID, BUTYRIC ACID, 4,4''-DITHIODIMORPHOLINE,2,2''-DITHIOBISBENZOTHIAZOLE AND MIXTURES THEREOF, IN A DRY CLEANINGSOLVENT.